Universal serial buses (USB), being the most popular transmission means today that can be disposed on various surfaces, can be adapted for almost all kinds of devices that are to be used for different operations, such as data transmission or charging, etc. For those USB sockets that are available today, they are usually being designed for an USB plug to plug into its USB connector in a direction vertical to the surface where it is being disposed. However, ergonomically, we are mostly accustomed to the plugging and pulling of the USB plug in a direction that forms an acute included angle with the surface on which the USB socket is disposed. In another word, the conventional USB sockets that allow a corresponding USB plug to plug in vertically is not conforming to the principle of ergonomic engineering, using which not only the plugging in of the USB plug is not easy to perform, but also both the USB socket and its corresponding USB plug can easily be damaged after being used for a period of time, since in most case, a user is used to and may carelessly force to plug an USB plug into a conventional USB socket in a direction that is not perpendicular thereto.